The　inhomogeneity　and　fatigue　properties　of　the　friction　stir　welded　butt　joints　for　2219-T6　aluminum　alloy　were　analyzed　by　metallographic　observation　of　different　zones,　fatigue　tests　and　micro-hardness　measurement.　The　results　show　that　the　lowest　hardness　and　fatigue　crack　initiation　sites　are　mainly　located　in　heat　affected　zone.　The　elastic-plastic　FE　model　was　established　based　on　the　micro-hardness,　microstructure　and　the　mechanical　properties　obtained　from　micro-tensile　tests　of　every　zone.　The　stress　and　strain　distributions　of　joints　were　simulated　under　cyclic　loading.　According　to　the　FE　simulations　results,　the　fatigue　lives　were　estimated　by　using　the　damage　equation　of　Smith-Watson-Topper　and　the　stress-strain　data　of　the　weak　area　in　the　joints.　The　results　of　estimations　are　compared　with　the　test　results　and　the　errors　are　less　than　two　times　of　factors.　©,　2014,　Science　Press.　All　right　reserved.